as I understand it, STK only has access to contacts stored on SIM, not the ones in the ME.

You are right.

Quote:

however, I have seen several references to handsets that support importing/exporting contacts to and from SIM using a STK application they provided to the operator.

does anyone know how they are doing this?

Have you ever seen any real implementation? Many phones have/used to have this import/export functionality but AFAIK it's non standard, something for user convenience - manually triggered. And then STK app is able to read SIM contacts. Maybe just a marketing mixing these?